The invention relates in general to automatic guided vehicles (AGVs) and, in particular, to methods and systems for navigating automatic guided vehicles through congested factory floors having intelligible areas for providing navigating information to the vehicles.
Presently, wire guidance systems and the like are widely used in which automatic guided vehicles are provided with sensors allowing the vehicles to accurately follow a path, e.g., wires embedded in the factory floor. These embedded wires are put in the floor such that they connect locations that the automatic guided vehicles will travel to and from. Such wire guidance systems typically provide as many as four different frequencies that sensors on the vehicle can detect to guide upon. In this manner complex patterns can be created which allow the vehicles to move in areas of high congestion. This type of guidance technology is very common and is used by a variety of vendors worldwide.
However, the wires buried in the floor do not indicate the location of individual automatic guided vehicles by themselves because the vehicle may be at any position along the wire. While bar coding, radio frequency identification (RFID) and other identification techniques have been used with automatic guided vehicles to identify their payloads or destinations, additional intelligence, i.e., information processing either centrally or on the vehicle, is required to direct the vehicles from one location to another and allow them to be tracked as they move so vehicle position, i.e., vehicle location, on the guidepath can be continually updated. For wire guidance technology, the vehicles must be able to select the proper guidance frequency as it moves, know when it is at its destination, and know when to hesitate to avoid other vehicles so collisions do not occur.
Typically the solution to this problem is provided by combining intelligence on the vehicles along with a central or host computer to control and monitor the vehicles. However, since many factories tend to be different in both physical layout and purpose, the guidepath that the vehicles follow may vary greatly. Therefore, this intelligence on the automatic guided vehicles' AGV computer and the central computer must be customized for each application or installation. Since the automatic guided vehicles are controlled by a computer, both the AGV computers and the central computer must have custom software written for each factory. It takes time to design, code and debug this software and it can be very expensive requiring substantial engineering man-hours to implement.
Automatic guided vehicles are usually dispatched to a location by one of three available options: (1) an individual physically retrieves a vehicle while it is circulating around a simple guide path "loop" which drastically limits the automatic guided vehicles capabilities and intended path of the automatic guided vehicle to simple movements; (2) the vehicle has an intended guide path and all possible routing information is stored on-board; or (3) an off-board, upper level control system routes a vehicle to a specific location.
If the proposed guide path of the automatic guided vehicle is complex, e.g., having multiple loops and intersections, then the vehicle must know when to turn, and how to turn for a given situation. All the required information needed to execute movement must be stored onboard the vehicle. Such information stored on the automatic guided vehicle would demand rather large and indefinate amounts of memory storage as the automated system expands. The stored information would be unique to that specific site installation. Costly additional programming would be required for each new installation. The complexity significantly increases when multiple automatic guided vehicle's are introduced into the system.
Alternatively, an off-board, upper level control system, commonly known as a "host," could generally be a programmable logic controller (PLC) or personal computer (PC) level of computer or higher. Movement commands from the host are relayed to the vehicle via an RF link or by other available means of communications. Hardware costs are added above and beyond the cost of the automatic guided vehicles. Again, information required to run the automated system would be unique to that specific site installation. Costly additional programming would be required for each new installation.